Potentially habitable super-Earth discovered with SPECULOOS telescopes

An international research team has identified two superterrestrial planets orbiting the star LP 890-9 using SPECULOOS telescopes.

LP 890-9, also known as TOI-4306 or SPECULOOS-2, is a small, cool star located about 100 light-years from our planet and is the second coolest star in which super-Earth planets have been discovered, after the famous TRAPPIST-1.

Excavation of super earth planets

The first super-Earth – LP 890-9b (or TOI-4306b) – is the innermost in the system and was first identified by NASA’s Transiting Exoplanet Survey Satellite (TESS), a mission to locate exoplanets orbiting nearby stars.

About 30% larger than Earth, LP 890-9b orbits its star in just 2.7 days. Researchers used their ground-based Search for habitable Planets EClipsing ULtra-cOOl Stars (SPECULOOS) telescopes to confirm and characterize this planet and probe the system for other planets that TESS may have missed.

Laetitia Delrez, astrophysicist at the University of Liège and leader of the study, said: “TESS uses the transit method to search for exoplanets by monitoring the brightness of thousands of stars simultaneously and looking for slight obscurations that could be caused by planets passing in front of their stars .

“However, follow-up with ground-based telescopes is often required to confirm the planetary nature of the discovered candidates and to refine measurements of their size and orbital properties.”

This tracking is essential for cold stars like LP 890-9 because they emit most of their light in the near-infrared, to which TESS has limited sensitivity. In contrast, SPECULOOS telescopes are optimized to observe these types of stars with high precision since their cameras are extremely sensitive to infrared.

Michaël Gillon, FNRS Senior Research Associate, Co-Director of the Astrobiology Research Unit at ULiège and Principal Investigator of the SPECULOOS project, commented: “The aim of SPECULOOS is to search for potentially habitable terrestrial planets passing the Sun’s smallest and coolest stars in the vicinity , like the TRAPPIST-1 planetary system that we discovered in 2016 thanks to a pilot project with our TRAPPIST South telescope.

“This strategy is motivated by the fact that such planets are particularly well suited for detailed studies of their atmosphere and the search for possible chemical traces of life with large observatories like the JWST.”

Findings from SPECULOOS

The SPECULOOS telescopes have not only confirmed Super-Earth’s first planet, but also identified an unknown second. Dubbed LP 890-9c (renamed SPECULOOS-2c by the ULiège researchers), this planet is 40% larger than Earth and has an orbital period of 8.5 days. This orbital period puts the super-Earth in the habitable zone of its star.

Francisco J. Pozuelos, researcher at the Institute of Astrophysics of Andalusia and co-author of the study, said: “Although this planet orbits its star very closely, at a distance about ten times shorter than that of Mercury around our sun, the amount of stellar radiation that it receives is still small and could allow for the presence of liquid water on the planet’s surface provided there is a sufficient atmosphere.”

“That’s because the star LP 890-9 is about 6.5 times smaller than the Sun and has a surface temperature half that of our star. This explains why LP 890-9c, despite being much closer to its star than Earth is to the Sun, could still have conditions suitable for life.”

The team is now attempting to analyze this planet’s atmosphere using instruments such as the JWST, for which LP 890-9c is the second most desirable target among potentially habitable terrestrial planets, surpassed only by the TRAPPIST-1 planets.

Delrez concludes: “However, this comparison does not take into account that LP 890-9c is close to the inner limit of the habitable zone and could therefore have a particularly water vapor-rich atmosphere, which would then amplify its atmospheric signals.

“Furthermore, depending on the properties of the star, the models often differ regarding the exact location of this inner limit of the habitable zone. Therefore, the discovery of LP 890-9c offers a unique opportunity to better understand and constrain the habitability conditions around the smallest and coolest stars in our solar neighborhood.”